The United States and Japan will step up their defence cooperation to deal with the threat from nuclear-armed North Korea as tensions in East Asia remain high, officials from the two allies said on Thursday.

WA police yet to speak with siege accused

Police are yet to speak to a man accused of terrorising five hostages before being shot in the face by heavily-armed officers after a two-hour siege in a Perth home.

Daniel Ashley, 26, remains in hospital in a critical but stable condition.

He faces serious charges including deprivation of liberty, assault and going armed to cause fear.

Police Minister Liza Harvey said she had been briefed on Wednesday's siege, which prompted a 200 metre exclusion zone around the Mosman Park house.

It's being investigated by the major crime squad and internal affairs unit.

"I thought the footage was terrifying and it was quite frightening for that community," Ms Harvey told reporters on Thursday .

"There's a lot of operational areas that I really don't want to go into, but that's what our police force are there for, that's what we fund them for and thankfully, we ask them to do these jobs to protect the community, so they can bring order to circumstances like this."